The increasing use of portable communication devices with newer rechargeable batteries has created a need for improved battery chargers. Examples of such communication devices are radiotelephones, radios, and modems. A typical battery charger charges at a high current rate until the battery is almost charged then reduces the charge rate to a low maintenance or trickle charge. It is important that the battery charger change from the high current rate to the trickle rate at the appropriate time or the battery's cycle life can be reduced. The change over time is usually determined by monitoring the battery temperature.
The new metal nickel hydride (NiMH) batteries will typically lose their charge over an extended period of time, even without use. Typically, the trickle charge is used to keep the battery fully charged until it is used. However, the manufacturers of NiMH batteries have suggested that the use of a trickle charge will reduce the battery's cycle life. Thus, there exists a need for an apparatus and method to maintain the charge of NiMH batteries without reducing the battery cycle life.